The present invention relates to a method of manufacturing a semiconductor device, and more particularly relates to a manufacturing method employing a thermosetting resin for packaging of the semiconductor device.
In a semiconductor market thick with competition, a semiconductor device is becoming smaller and cheaper. Encouraging the trend, much attention has now focused on mounting methods using a thermosetting resin in the mounting process of a semiconductor device. A thermosetting resin realizes fine pitch pattern mounting and easy processing. Above all, the most popular method is the chip mounting using an anisotropic conductive resin in which conductive particles disperse in the resin. Two different forms of the resin, anisotropic conductive films (called generally ACF) and anisotropic conductive paste (called generally ACP), are generally used for this mounting.
As shown in FIGS. 8A-8D, a conventional mounting process using such materials includes:
forming a layer of anisotropic conductive resin (thermosetting resin) (elements 11a and 11b) onto a substrate by either:
i) temporary press-bonding anisotropic conductive film 11a onto a substrate (FIG. 8A) or
ii) applying anisotropic conductive paste 11b on a substrate (FIG. 8B);
mounting semiconductor chip 2 on substrate 4 so as to align to the printed pattern thereon (FIG. 8C);
heating and press-bonding semiconductor chip 2 (FIG. 8D).
In the conventional mounting, however, the reliability of moisture resistance has not been sufficiently obtained due to lack of absolute contact between the semiconductor chip and the thermosetting resin.
That is, when heating and press-bonding in the step 8D, the chip and the substrate expand both by heat. At this moment, as a coefficient of linear expansion of the chip material differs from that of the substrate material, the difference causes a distortion at bonded portion by the time the chip and the substrate cool down to a normal temperature. As a result, a crack appears between the chip and the resin, or the substrate and the resin, permitting water intrusion, thereby the absolute contact of the resin to the chip or the substrate is hampered.
The present invention addresses the problem above. It is therefore an object of the present invention to provide an improved method of manufacturing a semiconductor device using a thermosetting resin by minimizing a distortion generated during the heating and press-bonding process. The method eliminates a crack between the chip and the resin, or the substrate and the resin, thus the reliability of moisture resistance is greatly improved.
The method of manufacturing a semiconductor device of the present invention comprises steps of:
i) forming a wiring pattern on a substrate;
ii) forming a thermosetting resin layer over the substrate so that the whole wiring pattern is covered therewith;
iii) aligning the electrode disposed on the bottom of the semiconductor chip for electric connections to the wiring pattern via the thermosetting resin layer; and
iv) press-bonding the electrode onto the substrate by applying heat from upper side of the chip, while the substrate is cooled.
According to the present invention, the substrate is cooled during the press-bonding step, so that the amount of thermal expansion of the substrate is suppressed. The material forming the substrate has a coefficient of linear expansion larger than that of the chip. By cooling the substrate, the difference between the amount of thermal expansion of the substrate and that of the chip becomes small. This reduces the distortion in the bonding layer, eliminating any crack that might develop between the chip and the resin, or between the substrate and the resin. As a result, the reliability of moisture resistance in the semiconductor device is greatly improved.